(part 4 of 6)

FERTILIZERS

Hemp requires an abundant supply of plant food. Attaining in four
months a height of 6 to 12 feet and producing a larger amount of dry
vegetable matter than any other crop in temperate climates, it must be
grown on a soil naturally fertile or enriched by a liberal application of
fertilizer. In Europe and in Asia heavy applications of fertilizers are
used to keep the soils up to the standard for growing hemp, but in the
United States most of the hemp is grown on lands the fertility of which has
not been exhausted by centuries of cultivation. In Kentucky, where the
farms are well stocked with horses and cattle, barnyard manure is used to
maintain the fertility of the soils, but it is usually applied to other
crops and not directly to hemp. In other States no fertilizer has been
applied to soils where hemp is grown, except in somewhat limited
experiments.
BARNYARD MANURE.---The best single fertilizer for hemp is
undoubtedly barnyard manure. It supplies the three important plant foods,
nitrogen, potash, and phosphoric acid, and it also adds to the store of
humus, which appears to be more necessary for hemp than for most other farm
crops. If other fertilizers are used, it is well to apply barnyard manure
also, but it should be applied to the preceding crop, or, at the latest, in
the fall before the hemp is sown. It must be well rotted and thoroughly
mixed with the soil before the hemp seed is sown, so as to promote a
uniform growth of the hemp stalks. Uniformity in the size of the plants of
other crops is of little consequence, but in hemp it is a matter of prime
importance. An application of coarse manure in the spring, just before
sowing, is likely to result in more injury than benefit. The amount that
may be applied profitably will vary with different soils. There is little
danger, however, of inducing too rank a growth of hemp on upland soils,
provided the plants are uniform, for it must be borne in mind that stalk
and not fruit is desired. On soils deficient in humus as the result of
long cultivation, the increased growth of hemp may well repay for the
application of 15 to 20 tons of barnyard manure per acre. It would be
unwise to sow hemp on such soils until they had been heavily fertilized
with barnyard manure.

COMMERCIAL FERTILIZERS.---On worn-out soils, peaty soils, and
possibly on some alluvial soils, commercial fertilizers may be used with
profit in addition to barnyard manure. The primary effect to be desired
from commercial fertilizers on hemp is a more rapid growth of the crop
early in the season. This rapid early growth usually results in a greater
yield and better quality of fiber. The results of a series of experiments
conducted at the agricultural experiment station at Lexington, Ky., in 1889
led to the following conclusions: (Scovel, M.A. Effect of Commercial
Fertilizers on Hemp. Kentucky Agricultural Experiment Station, Bulletin
27, p. 3, 1890.)
(1) That hemp can be raised successfully on worn bluegrass soils
with the aid of commercial fertilizers.
(2) That both potash and nitrogen are required to produce the best
results.
(3) That the effect was the same, whether muriate or sulphate was
used to furnish potash.
(4) That the effect was about the same, whether nitrate of soda or
sulphate of ammonia was used to furnish nitrogen.
(5) That a commercial fertilizer containing about 6 per cent of
available phosphoric acid, 12 per cent of actual potash, and 4 per cent of
nitrogen (mostly in the form of nitrate of soda or sulphate of ammonia)
would be a good fertilizer for trial.

The increased yield and improved quality of the fiber on the
fertilized plats compared with the yield from the check plat, not
fertilized, in these experiments would warrant the application of nitrogen
at the rate of 160 pounds of nitrate of soda or 120 pounds of sulphate of
ammonia per acre, and potash at the rate of about 160 pounds of either
sulphate or muriate of potash per acre.
On the rich alluvial soils reclaimed by dikes from the Sacramento
River at Courtland, Cal., Mr. John Heaney has found that an application of
nitrate of soda at the rate of not more than 100 pounds per acre soon after
sowing and again two weeks to a month later, or after the first application
has been washed down by rains, will increase the yield and improve the
quality of the fiber.

LEGUMINOUS CROPS OR GREEN MANURE.---Beans grown before hemp and the
vines returned to the land and plowed under have given good results in
increased yield and improved quality of fiber on alluvial soils at
Courtland, Cal. Clover is sometimes plowed under in Kentucky to enrich the
land for hemp. It must be plowed under during the preceding fall, so as to
become thoroughly rotted before the hemp is grown.
HEMP AS A GREEN MANURE.---In experiments with various crops for
green manure for wheat in India, hemp was found to give the best results.
(Report of Cawnpore Agricultural Station, United Provinces, India, for
1908, p. 12.) In exceptionally dry seasons, as in 1908 and 1913, many
fields of hemp do not grow high enough to be utilized profitably for fiber
production. They are often left until fully mature and then burned.
Better results would doubtless be obtained if the hemp were plowed under as
soon as it could be determined that it would not make a sufficient growth
for fiber production. Mature hemp stalks or dry hurds should not be plowed
under, because they rot very slowly.

DISEASES, INSECTS, AND WEEDS.

Hemp is remarkably free from diseases caused by fungi. In one
instance at Havelock, Nebr., in a low spot where water had stood, nearly 3
per cent of the hemp plants were dead. The roots of these dead plants
were pink in color and a fungous mycelium was found in them, but it was not
in a stage of development to permit identification. The fungus was
probably not the primary cause of the trouble, since the dead plants were
confined to the low place and there was no recurrence of the disease on
hemp grown in the same field the following year.
A fungus described under the name Dendrophoma marconii Cav. was
observed on hemp in northern Italy in 1887. (Cavara, Fridiano. Appunti di
Patologia Vegetal. Atti dell' Instituto Botanico dell' Universita di
Pavia, s. 2, v. 1, p. 425, 1888.) This fungus attacked the plants after
they were mature enough to harvest for fiber. Its progress over the plant
attacked and also the distribution of the infection over the field were
described as very rapid, but if the disease is discovered at its inception
and the crop promptly harvested it causes very little damage.
In the fall of 1913 a disease was observed on seed hemp grown by
the Department of Agriculture at Washington. (Pl. XLIII, fig. 2.) It did
not appear until after the stage of full flowering of the staminate plants
and therefore after the stage for harvesting for fiber. A severe hailstorm
had bruised the plants and broken the bark, doubtless making them more
susceptible to the disease. The first symptoms noted in each plant
attacked were wilted leaves near the ends of branches above the middle of
the plant, accompanied by an area of discolored bark on the main stalk
below the base of each diseased branch. In warm, moist weather the disease
spread rapidly, killing a plant 10 feet high in five days and also
infesting other plants. It was observed only on pistillate plants, but the
last late-maturing staminate plants left in the plat after thinning the
earlier ones were cut soon after the disease was discovered. (This fungus
was not in a stage permitting identification, but cultures for further
study were made in the Laboratory of Plant Pathology.)

In a few instances insects boring in the stems have killed some
plants, but the injury caused in this manner is too small to be regarded as
really troublesome.
Cutworms have caused some damage in the late-sown hemp in land
plowed in the spring, but there is practically no danger from this source
in hemp sown at the proper season and in fall-plowed land well harrowed
before sowing.
A Chilean dodder (Cuscuta racemosa) troublesome on alfalfa in
northern California was found on the hemp at Gridley, Cal., in 1903.
Although it was abundant in some parts of the field at about the time the
hemp was ready for harvest, it did not cause any serious injury.
Black bindweed (Polygonum convolvulus) and wild morning-glory
(Convolvulus sepium) sometimes cause trouble in low, rich land by climbing
up the plants and binding them together.

The only really serious enemy to hemp is branched broom rape
(Orobanche ramosa). (Pl. XLIII, fig. 3.) This is a weed 6 to 15 inches
high, with small, brownish yellow, scalelike leaves and rather dull purple
flowers. The entire plant is covered with sticky glands which catch the
dust and give it a dirty appearance. Its roots are parasitic on the roots
of hemp. It is also parasitic on tobacco and tomato roots. (Garman, H.
The Broom-Rape of Hemp and Tobacco. Kentucky Agricultural Experiment
Station, Bulletin 24, p. 16, 1890.) Branched broom rape is troublesome in
Europe and the United States, but is not known in Asia. Its seeds are very
small, about the size of tobacco seed, and they stick to the gummy calyx
surrounding the hemp seed when the seed-hemp plants are permitted to fall
on the ground in harvesting. There is still more opportunity for them to
come in contact with the seed of hemp grown for fiber. The broom rape is
doubtless distributed more by means of lint seed (seed from overripe fiber
hemp) than by any other means. When broom rape becomes abundant it often
kills a large proportion of the hemp plants before they reach maturity. As
a precaution it is well to sow only well-cleaned seed from cultivated hemp
and insist on a guaranty of no lint seed. If the land becomes infested,
crops other than hemp, tobacco, tomatoes, or potatoes should be grown for a
period of at least seven years. The seeds retain their vitality several
years. ( Garman, H. The Broom-Rapes. Kentucky Agricultural Experiment
Station, Bulletin 105, p. 14, 1903.)

HEMP-SEED PRODUCTION.

All of the hemp seed used in the United States for the production
of hemp for fiber is produced in Kentucky. Nearly all of it is obtained
from plants cultivated especially for seed production and not for fiber.
The plants cultivated for seed for the fiber crop are of the
fiber-producing type and not the type commonly obtained in bird-seed hemp.
Old stocks of hemp seed of low vitality are often sold for bird seed, but
much of the hemp seed sold by seedsmen or dealers in bird supplies is of
the densely branching Smyrna type.

LINT SEED.

In some instances seed is saved from hemp grown for fiber but
permitted to get overripe before cutting. This is known as lint seed. It
is generally regarded as inferior to seed from cultivated plants. A good
crop is sometimes obtained from lint seed, but it is often lacking in vigor
as well as germinative vitality, and it is rare that good crops are
obtained from lint seed of the second or third generation.

CULTIVATED SEED.

Nearly all of the cultivated seed is grown in the valley of the
Kentucky River and along the creeks tributary to this river for a distance
of about 50 miles above High Bridge. The river through this region flows
in a deep gorge about 150 feet below the general level of the land. The
sides of this valley are steep, with limestone outcropping, and in some
places perpendicular ledges of lime rock in level strata. (Pl. XLII, fig.
3.) The river, which overflows every spring, almost covering the valley
between the rocky walls, forms alluvial deposits from a few rods to half a
mile in width. The seed hemp is grown on these inundated areas, and
especially along the creeks, where the water from the river backs up,
leaving a richer deposit of silt than along the banks of the river proper,
where the deposited soils are more sandy. There is a longer season free
from frost in these deep valleys than on the adjacent highlands. Instead
of having earlier frosts in the fall, as may be usually expected in
lowlands, the valley is filled with fog on still nights, thus preventing
damage from frost. For the production of hemp seed a rich, alluvial soil
containing a plentiful supply of lime and also a plentiful supply of
moisture throughout the growing season is necessary. The crop also
requires a long season for development. The young seedlings will endure
light frosts without injury, but a frost before harvest will nearly ruin
the crop. A period of dry weather is necessary after the harvest in order
to beat out and clean the seeds.

PREPARATION OF LAND.

The land is plowed as soon as possible after the spring floods,
which usually occur in February and early in March. After harrowing, it is
marked in checks about 4 or 5 feet each way. Hemp cultivated for seed
production must have room to develop branches. (Pl. XL, fig. 1.)

PLANTING.

The seed is planted between the 20th of March and the last of
April---usually earlier than the seed is sown for the production of fiber.
It is usually planted by hand, 5 to 7 seeds in a hill, and covered with a
hoe. In some instances planters are used, somewhat like those used for
planting corn, and on some farms seeders are used which plant 1 or 2 drills
at a time 4 or 5 feet apart. When planted in drills it is usually
necessary to thin out the plants afterwards. One or two quarts of seed are
sufficient to plant an acre. Less than one quart would be sufficient if
all the plants were allowed to grow.

CULTIVATION.

On the best farms the crop is cultivated four times---twice rather
deep and twice with cultivators with fine teeth, merely stirring the
surface. When the first flowers are produced, so that the staminate plants
may be recognized, all of these plants are cut out except about one per
square rod. These will produce sufficient pollen to fertilize the flowers
on the pistillate, or seed-bearing plants, and the removal of the others
will give more room for the development of the seed-bearing plants.

HARVEST.

The seed-bearing plants are allowed to remain until fully mature,
or as long as possible without injury from frost. They are cut with corn
knives, usually during the first half of October, leaving the stubble 10 to
20 inches high. The plants are set up in loose shocks around one or two
plants which have been left standing. The shocks are usually bound near
the top with binder twine. They are left in this manner for two or three
weeks, until thoroughly dry. (Pl. XLIII, fig. 1.)

COLLECTING THE SEED.

When the seed hemp is thoroughly dry, men (usually in gangs of
five or six, with tarpaulins about 20 feet square) go into the field. One
man with an ax cuts off the hemp stubble between four shocks and clears a
space large enough to spread the tarpaulin. The other men pick up an
entire shock and throw it on the tarpaulin. They then beat off the seeds
with sticks about 5 feet long and 1 1/2 inches in diameter. (Pl. XLIV.
fig. 1.) When the seed has been beaten off from one side of the shock the
men turn it over by means of the sticks, and after beating off all of the
seed they pick up with the sticks the stalks in one bunch and throw them
off the canvas, and then treat another shock in the same manner. They will
beat off the seed from four shocks in 15 to 20 minutes, securing 2 or 3
pecks of seed from each shock. While this seems a rather crude way of
collecting the seed, it is doubtless the most economical and practical
method that may be devised. The seed falls so readily from the dry hemp
stalks that it would be impossible to move them without a very great loss.
Furthermore, it would be very difficult to handle plants 10 to 14 feet
high, with rigid branches 3 to 6 feet in length, so as to feed them to any
kind of thrashing machine.

CLEANING THE SEED.

The seed and chaff which have been beaten on the tarpaulin are
sometimes beaten or tramped to break up the coarser bunches and stalks, and
in some instances they are rubbed through coarse sieves in order to reduce
them enough to be put through a fanning mill. The seed is then partly
cleaned by a fanning mill in the field and afterwards run once or twice
through another mill with finer sieves and better adjustments of fans.
Even after this treatment it is usually put through a seed-cleaning machine
by the dealers. There has recently been introduced on some of the best
seed-hemp farms a kind of homemade thrashing machine, consisting
essentially of a feeding device, cylinder, and concaves, attached to a
rather large fanning mill, all being driven by a gasoline engine. (Pl.
XLIV, fig. 2.) The hemp seed is fed to this machine just as it comes from
the tarpaulin after beating off from the shock. It combines the process of
breaking up the chaff into finer pieces and the work of fanning the seed in
the field, and it performs this work more effectively and more rapidly.

YIELD.

Under favorable conditions the yield of hemp seed ranges from 12 to
25 bushels per acre. From 16 to 18 bushels are regarded as a fair average
yield.

COST OF SEED PRODUCTION.

The hemp-seed growers state that it costs about $2.50 per bushel to
produce hemp seed, counting the annual rental of the land at about $10 per
acre. With the introduction of improved machinery for cleaning the hemp
this cost may be somewhat reduced, since it is estimated that with the
ordinary methods of rubbing the seed through sieves or beating it to reduce
the chaff to finer pieces the cost from beating it off the shock to
delivering it at the market is about 50 cents per bushel. These estimates
of cost are based on wages at $1.25 per day.

PRICES.

The price of hemp seed, as sold by the farmer during the past 10
years, has ranged from $2.50 to $5 per bushel. The average farm price
during this period has been not far from $3 per bushel. Hemp seed is sold
by weight, a bushel weighing 44 pounds.

CULTIVATION FOR FIBER.

PREPARATION OF THE LAND.

Fall plowing on most soils is generally regarded as best for hemp,
since the action of the frost in winter helps to disintegrate the particles
of soil, making it more uniform in character. In practice, hemp land is
plowed at any time from October to late seeding time in May, but hemp
should never be sown on spring-plowed sod. The land should be plowed 8 or
9 inches in order to give a deep seed bed and opportunity for root
development. Plowing either around the field or from the center is
recommended, since back furrows and dead furrows will result in uneven
moisture conditions and more uneven hemp. Before sowing, the land is
harrowed to make a mellow seed bed and uniform level surface. Sometimes
this harrowing is omitted, especially when hemp is grown on stubble ground
plowed just before seeding. Harrowing or leveling in some manner is
recommended at all times, in order to secure conditions for covering the
seed at a uniform depth and also to facilitate close cutting at harvest
time.

SEEDING.

METHODS OF SEEDING.

Hemp seed should be sown as uniformly as possible all over the
ground and covered as nearly as possible at a uniform depth of about
three-fourths of an inch, or as deep as 2 inches in light soils. Ordinary
grain drills usually plant the seed too deeply and in drills too far apart
for the best results. Uniform distribution is sometimes secured by
drilling in both directions. This double working, especially with a disk
drill, leaves the land in good condition. Ordinary grain drills do not
have a feed indicator for hemp seed, but they may be readily calibrated,
and this should be done before running the risk of sowing too much or too
little. Fill the seed box with hemp seed, spread a canvas under the
feeding tubes, set the indicator at a little less than one-half bushel per
acre for wheat, and turn the drivewheel as many times as it would turn in
sowing one-tenth acre. One method giving good results is to remove the
lower sections of the feeding tubes on grain drills and place a flat board
so that the hemp seed falling against it will be more evenly distributed,
the seed being covered either by the shoes of the drill or by a light
barrow. Good results are obtained with disk drills, roller press drills,
and also with the end-gate broadcast seeder. Drills made especially for
sowing hemp seed are now on the market, and they are superseding all other
methods of sowing hemp seed in Kentucky. Rolling after seeding is advised,
in order to pack the soil about the seed and to secure a smooth surface for
cutting, but rolling is not recommended for soils where it is known to have
an injurious effect.

AMOUNT OF SEED.

Hemp is sown at the rate of about 3 pecks (33 pounds) per acre.
On especially rich soil 1 1/2 bushels may be sown with good results, and on
poor land that will not support a dense, heavy crop a smaller amount is
recommended. If conditions are favorable and the seed germinates 98 to 100
per cent, 3 pecks are usually sufficient.
When kept dry, hemp seed retains its germinative vitality well for
at least three or four years, but different lots have been found to vary
from 35 to 100 per cent, and it is always well to test the seed before
sowing.

TIME OF SEEDING.

In Kentucky, hemp seed is sown from the last of March to the last
of May. The best results are usually obtained from April seeding. Later
seedings may be successful when there is a plentiful rainfall in June. In
Nebraska, hemp seed was sown in April, May, or sometimes as late as June.
In California it is sown in February or March; in Indiana and Wisconsin,
in May. In general, the best time for sowing hemp seed is just before the
time for sowing oats in any given locality.
After the seed is sown, the hemp crop requires no further care or
attention until the time of harvest.

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